Conscribed in 1997, he attended Ecole nationale des sous-officiers d’active (ENSOA) at Saint-Maixent. He was appointed sergeant and sent to the 2nd Marine Infantry Regiment (RIMa) after having passed Ecole d’application de l’Infanterie of Montpellier and taken part in several overseas operations as cell head.

In 2002, he was admitted to Ecole militaire interarmes (EMIA). Three years later, upon becoming officer, he chose the Engineering corps and was sent to the 2nd Foreign Engineering Regiment (2nd REG). Promoted captain on August 1, 2008, he took over the command of the 3rd mechanized combat company in June 2010, before leaving for Afghanistan in November 2010.

On December 17, 2010, during a reconnaissance mission for the construction of a position for the Afghan national army, a fight erupted with the rebels. Captain Dupin, in his capacity of commander of the GTIA Kapisa engineering company, was one of three French soldiers, of the unit composed of some fifty French, American, Romanian and Afghan soldiers who were preparing for the creation of a security position. Protection soldiers retaliated the attack with mortar shots backed by air support. The GTIA Kapisa rapid intervention force intervened and inflicted losses on the attackers, and they were forced to withdraw. Captain Dupin was seriously wounded during the operation. He was aged 34.

Captain Benoît Dupin, who died for France, had carried out several overseas operations during his career (Bosnia, Kosovo, Djibouti, and Chad). His biography disseminated by the infantry headquarters portrays him as a strict officer: "Pugnacious, Captain Benoît Dupin is a pernickety and methodical officer. Taking no chances, he remarkably prepared his unit throughout operational briefing prior to his departure for any overseas operation."

He was an exemplary officer to go by his moral qualities, he was married and father of a young boy.